Gear pump

ABSTRACT

An internal-external gear pump having a crescent member opposite the mesh point of the gears for preventing direct fluid communication between the inlet and outlet ports. The crescent has a leading edge adjacent the inlet port which simultaneously seals the spaces between the gear teeth from the zero displacement interval of the inlet port as the gears rotate past the leading edge.

Langenderf er GEAR PUMP [75] Inventor: lLes M. Langenderfer, Toledo, Ohio [73] Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: Aug. 23, 1972 211 App]. No.: 282,924

[52] US. Cl. 418/170 [51] Int. Cl. ..1F01c 11/10, F03c 3/00, F04C 1/06 [58] Field of Search 418/126; 169, 170

[56] References Cited UNITED STATES PATENTS 3,096,720 7/1963 Younger 418/170 3,204,564 9/1965 Eltze 418/170 FOREIGN PATENTS OR APPLICATIONS 3,526 0/1882 Great Britain 418/170 1 Jan. 15, 1974 3,801 0/1888 Great Britain v.418/169 291,208 12/1931 Italy 418/169 Primary ExaminerCarlton R. Croyle Assistant Examiner.1ohn J. Vrablik Att0rneyW. E. Finken et a1.

' 57 ABSTRACT An internal-external gear pump having a crescent member opposite the mesh point of the gears for preventing direct fluid communication between the inlet and outlet ports. The crescent has a leading edge adjacent theinlet port which simultaneously seals the spaces between the gear teeth from the zero displacement interval of the inlet port as the gears rotate past the leading edge.

2 Claims, 2 Drawing Figures GEAR PUMP This invention relates to fluid pumps and more particularly to internal-external gear pumps.

Internal-external gear pumps incorporate a crescent member between the gears opposite the'mesh point of the gears. The function of the crescent member is to prevent direct fluid communication between the inlet and outlet ports of the pump. Internal-external gear pumps have an interval of zero displacement which occurs at the inlet port. This zero displacement interval is the time during which the gear teeth are coming out of mesh until the gear teeth arrive at a sealing relationship with the crescent member.

The present invention includes a leading edge on the crescent member adjacent the inlet port, which leading edge is shaped to simultaneously end the zero displacement interval for the teeth on both the internal and external gear. Gear pumps incorporating this invention exhibit a higher overall efficiency than similarly designed gear pumps having the leading edge of the crescent positioned perpendicular to the inlet fluid flow.

It is an object of this invention to provide in an improved internal-external gear pump a crescent member having a leading edge shaped to simultaneously close the zero displacement interval for the teeth on both gears.

It is another object of this invention to provide in an improved internal-external gear pump a crescent member having a leading edge adjacent to the inlet port which will simultaneously seal .the space between the teeth from the inlet port as the gear teeth are rotated past the leading edge.

These and other objects and advantages will be more apparent from the following description and drawings in which:

FIG. 1 is a sectional elevational view of a pump incorporating the invention: and

FIG. 2 is a graph depicting the efficiency of a pump incorporating the invention.

Referring to the drawings, there is shown in FIG. 1 an externally toothed gear 10 meshing with an internally toothed gear 12 which is rotatably disposed in a pump housing 14. The gears l and 12 are in full mesh along line 16 at point 16a. The gear is drivingly connected to a drive shaft 18 by a pair of tangs 20 which are disposed in slots 22 on the drive shaft 18. The drive shaft 18 is adapted to be driven by an engine or torque connector impeller, not shown.

The pump housing 14 has formed therein an inlet fluidport 24 and an outlet fluid port 26. A crescent member 28 is formed integrally with or otherwise secured to the pump housing 14 and extends between the inlet port 24 and the outlet port 26between the teeth on gears 10 and 12 diametrically opposite the mesh point Ida of the gears. The crescent member 28 has a trailing edge 30 adjacent the outlet port 26 and a leading edge 32 adjacent the inlet port 24. The leading edge 32 is shaped such that teeth 34 on gear 10 and teeth 36 on gear 12 will simultaneously be rotated into sealing contact with the crescent member 28. The gear teeth on the gears 10 and 12 remain in sealing relationship with the crescent 28 until they are rotated past the trailingedge 3th at which time the space between the teeth are open to the outlet port 26. The fluid carried in the spaces between the gear teeth is expelled from the outlet port as the gear teeth are rotated into mesh between the trailing edge 30 and the point 16a of full mesh.

Fluid is admitted between the gears while the gears are being rotated and the teeth therein come out of mesh between the point 16a of full mesh and the leading edge 32 of the crescent 28. The interval of rotation between when the teeth are fully out of mesh, for example at point 38, and when the teeth engage the leading edge 32 of the crescent member 28is termed a zero displacement interval. A zero displacement interval also occurs during the pumping cycle. between the interval when the teeth arerotated out of sealing contact with the trailing edge 30 and a point where the teeth begin to mesh adjacent the outer port 26.

The curve 40 shown in FIG. 2 depicts the overall efficiency of a gear pump incorporating a leading edge of the crescent which simultaneously seals the gear teeth at the close of the zero displacement interval. The curve 42 represents the efficiency of a gear pump incorporating a conventional leading edge on the crescent member which is disposed perpendicular to the fluid flow in the area of the inlet port. As can be seen from these curves a pump incorporating the present invention provides a higher overall efficiency and therefore reduces the input horsepower required for a given pump output.

Obviously, many modifications and variations are possible in the lightof the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A gear pump comprising; an inlet fluid port; and outlet fluid port; an externally toothed gear; an internally toothed gear of larger pitch diameter than said externally toothed gear and having a portion thereof meshing with said externally toothed gear and being eccentrically mounted relative thereto; drive means for rotating said externally toothed gear; and crescent means disposed in sealing relations between said gears adjacent the toothed peripheries thereof opposite the mesh point for preventing direct fluid communication between said fluid ports including a trailing edge adjacent said outlet fluid port and a leading edge adjacent said inlet fluid port, said leading edge being shaped to simultaneously sealingly contact the leading edges of the teeth on the internally and externally toothed gears as the gear teeth are rotated past said leading edge of said crescent means to simultaneously seal the space between the leading edges of the teeth and the trailing edges of the preceeding teeth on said internally and externally toothed gears from said inlet fluid port.

2. A gear pump comprising; an inlet fluid port; an outlet fluid port; an externally toothed gear; an internally toothed gear of larger pitch diameter than said externally toothed gear and having a portion thereof meshing with said externally toothed gear and being eccentrically mounted relative thereto; drive means for rotating said gears; said gear teeth being rotated through a zero displacement interval during the inlet portion of the pumping cycle; and crescent means disposed in sealing relation between said gears adjacent the toothed peripheries thereof opposite said mesh point for preventing direct fluid communication be tween said fluid port including a trailing edge adjacent said outlet fluid port and a leading edge adjacent said inlet fluid port, said leading edge defining the close of the zero displacement interval and being shaped to simultaneously sealingly contact the leading edges of the teeth on the internally and externally toothed gears as the gear teeth are rotated past said leading edge of said crescent means to simultaneously seal the space between the leading edges of the teeth and the trailing edges of the preceeding teeth on said internally and externally toothed gears. 

1. A gear pump comprising; an inlet fluid port; and outlet fluid port; an externally toothed gear; an internally toothed gear of larger pitch diameter than said externally toothed gear and having a portion thereof meshing with said externally toothed gear and being eccentrically mounted relative thereto; drive means for rotating said externally toothed gear; and crescent means disposed in sealing relations between said gears adjacent the toothed peripheries thereof opposite the mesh point for preventing direct fluid communication between said fluid ports including a trailing edge adjacent said outlet fluid port and a leading edge adjacent said inlet fluid port, said leading edge being shaped to simultaneously sealingly contact the leading edges of the teeth on the internally and externally toothed gears as the gear teeth are rotated past said leading edge of said crescent means to simultaneously seal the space between the leading edges of the teeth and the trailing edges of the preceeding teeth on said internally and externally toothed gears from said inlet fluid port.
 2. A gear pump comprising; an inlet fluid port; an outlet fluid port; an externally toothed gear; an internally toothed gear of larger pitch diameter than said externally toothed gear and having a portion thereof meshing with said externally toothed gear and being eccentrically mounted relative thereto; drive means for rotating said gears; said gear teeth being rotated through a zero displacement interval during the inlet portion of the pumping cycle; and crescent means disposed in sealing relation between said gears adjacent the toothed peripheries thereof opposite said mesh point for preventing direct fluid communication between said fluid port including a trailing edge adjacent said outlet fluid port and a leading edge adjacent said inlet fluid port, said leading edge defining the close of the zero displacement interval and being shaped to simultaneously sealingly contact the leading edges of the teeth on the internally and externally toothed gears as the gear teeth are rotated past said leading edge of said crescent means to simultaneously seal the space between the leading edges of the teeth and the trailing edges of the preceeding teeth On said internally and externally toothed gears. 